Single-Walled Carbon Nanotubes are one-dimensional nanometer-diameter molecular wires that have unique electrical, mechanical, electro-optical and electromechanical properties. As such, these nanotubes show promise as potential building blocks for future nanoscale electronic devices, such as field emitting devices, field-effect-transistors, single-electron-transistors, molecular sensors, and the like.
Single-Walled Carbon Nanotube based-devices can be prepared by deposition of a nanotube suspension on substrates, or via carbon vapor deposition (CVD) growth of individual nanotubes directly on substrates. The direct CVD growth method typically provides individual Single-Walled Carbon Nanotubes with few structural defects, while the preparation of Single-Walled Carbon Nanotube based-devices via deposition of a nanotube suspension on substrates usually results in Single-Walled Carbon Nanotubes which exist in bundles or single tubes of submicron lengths and which can have defects arising from post-synthetic destructive treatments. As such, the preparation of Single-Walled Carbon Nanotubes using the CVD growth method enjoys certain advantages over the nanotube suspension method and would appear to be the method of choice for large-scale fabrication of Single-Walled Carbon Nanotubes. But using the CVD growth method in the absence of external guidance methods typically yields short and randomly oriented nanotubes. For the purposes of fundamental study or device fabrication, it would be ideal to develop methods for making Single-Walled Carbon Nanotubes which allow for control over diameter, helicity, orientation and length.
Recent progress has been made in developing methods for the surface growth of Single-Walled Carbon Nanotubes wherein there is a slight degree of control over the diameter and orientation of the nanotubes being produced. It has been reported that a correlation exists between the size of the catalyst nanoparticles used and the diameter of the Single-Walled Carbon Nanotubes that are produced. As such, some control over the diameter of growing tubes has been realized by depositing uniform and monodisperse catalyst nanoparticles on substrates. In addition, it has also been reported that some degree of control over the orientation of Single-Walled Carbon Nanotubes could be achieved via the use of an external electric field during a CVD process, and this alignment effect is believed to originate from the high polarizability of the nanotubes. However, neither fabricating a microelectrode array nor introducing a strong electric field during the CVD growth is easy, especially for the large-scale fabrication. Lately, a fast heating process was reported that allows the growth of long (mm in length) and well-oriented Single-Walled Carbon Nanotubes by CVD using carbon monoxide as a carbon feedstock.
Thus, there still exists a need in the art for methods of making Single-Walled Carbon Nanotubes which allow a higher degree of control over various physical parameters of the nanotubes as they are made. This invention addresses that need.